Experimental determination of solubility parameters of oils as a function of pressure

In this work, the solubility parameter of dead and live crude oils was measured at 303.15 K and up to 300 bar, using the internal pressure approach. An indirect technique was chosen, using thermal expansivities (determined from microcalorimetric measurements) and isothermal compressibilities (calculated from density measurements). This method was tested on seven pure compounds, and the deviation with literature data is <1 MPa1/2. A method based on the refractive index was used to examine the validity of the results for the oils, and a deviation of <0.8 MPa1/2 was observed. A modified solubility parameter was also calculated from two cubic equations of state and compared to experimental results. In this case, the deviations are larger (up to 6.5 MPa1/2), whereas this approach gives accurate results for pure compounds. This might be due to the characterization procedure, because the volumes are measured and given as input. Therefore, a more appropriate characterization method should give better results.